The present invention relates to a medical stimulator which provides an electrical stimulation signal, in the form of a continuous or interrupted train of pulses to a patient. More particularly, the present invention relates to a medical stimulator with an intensity control which allows the patient to vary the intensity of the stimulation signals produced by the stimulator.
Medical stimulators which provide electrical stimulation signals to a patient are used to provide short and long term pain relief though transcutaneous electrical nerve stimulation (TENS) and to stimulate and rehabilitate muscles through neuromuscular stimulation (NMS). These types of medical stimulators typically use electrodes which are attached to the patient's skin. The TENS or NMS stimulator sends electrical stimulation signals into the muscles and nerves through the attached electrodes. The electrical stimulation signals produced by a TENS or NMS stimulator are in the form of a train of electrical pulses which may be modulated in rate and/or intensity. Medical stimulators commonly use periodic treatment modes for various reasons, such as to reduce accommodation and to reduce fatigue which can be produced by a continuous train of stimulation pulses. The periodic treatment modes generally have an on time and an off time cycle. A train of pulses forming the stimulation signal is delivered during the on time, and no pulses are delivered during the off time. The length of the on time and the off time may vary from mode to mode, and the rate and intensity of the pulses delivered during on time may also vary from mode to mode.
Many medical stimulators also provide a continuous mode in which a continuous train of pulses is provided as an output. The continuous mode is usually provided for initially setting the intensity of the stimulation. During treatment, the patient can increase or decrease the intensity at any time using an intensity control on the stimulator.
If the intensity is increased while the stimulator is operating in a periodic treatment mode and is in the "off time" of the cycle, or during a reduced stimulation time in a modulation mode, the patient cannot initially feel the increased intensity. When the stimulator switches to the "on time" portion of the cycle, or to the full stimulation time during a modulation mode, the patient can be unpleasantly surprised by the onset of the full intensity stimulation.
In the past, some stimulators have disabled the intensity control while the stimulator is operating in a periodic treatment or modulation mode. This can be frustrating to the patient, who wants to adjust the intensity while the stimulator is operating. The alternative has been to allow the patient to change the intensity at any time, with the risk being an unpleasant surprise if the intensity is adjusted during a off time or a reduced stimulation time.